The present invention relates to apparatus for cross-winding a traveling yarn on a bobbin, and more particularly, to yarn winding apparatus of this type wherein the bobbin is peripherally driven by a winding drum and a yarn guide traverses the traveling yarn along the bobbin to apply the yarn thereon in a cross-wound fashion.
In yarn cross-winding apparatus of the aforementioned type, a common disadvantage is the tendency of yarn to be wound more densely at the ends of the bobbin, which is particularly problematic in the production of dye bobbins wherein the yarn winding density should be as low as possible to facilitate the yarn dyeing process. To achieve this objective, yarn should be wound with an appropriately sharp crossing angle. However, the use of a relatively sharp crossing angle for this purpose tends to cause the yarn to draw axially inwardly with respect to the lengthwise extent of the bobbin at its opposite ends whereat the reversal of yarn cross-winding occurs. As a result, the yarn windings compact at the axial ends of the bobbin so that the effective axial extent of the yarn windings on the bobbin is shorter than that prescribed by the traversing yarn guide and, in turn, only the central extent of the yarn windings on the bobbin have the desired low density with the axial ends of the bobbin being more densely formed than desirable. Further, this problem cannot be compensated by enlarging the yarn traversal, which only serves to form the densified windings of yarn at a greater spacing from one another. The yarn windings at the opposite ends of the bobbin still tends to move axially inwardly with a relatively flattened reversal angle so that the yarn is still more densely wound at the bobbin ends.
West German Offenlegungsschrift 22 42 507 discloses a yarn winding apparatus of the aforementioned type wherein the winding drum which frictionally drives the bobbin is formed with a central peripheral area which is substantially smooth and with peripheral areas at the opposite ends formed with concentric or helical grooves to assist in applying the yarn to the ends of the bobbin during winding. However, the use of such an arrangement of grooves on the winding drum requires that the winding drum and the traversing yarn guide must be synchronized with one another so that a groove of the winding drum is properly located at the point of yarn contact with the bobbin when the traversing yarn guide reaches each opposite end of its traversing movement. As a result, certain set translation ratios must be maintained between the winding drum and the traversing yarn guide and, in turn, the possible range of selective adjustment of the desired yarn cross-winding angle is reduced.